A gas turbine engine typically includes a compressor section, a combustor, and a turbine section. The compressor section compresses ambient air that enters an inlet. The combustor combines the compressed air with a fuel and ignites the mixture creating combustion products defining a working fluid. The working fluid travels to the turbine section where it is expanded to produce a work output. Within the turbine section are rows of stationary vanes directing the working fluid to rows of rotating blades coupled to a rotor. Each pair of a row of vanes and a row of blades form a stage in the turbine section.
Advanced gas turbines with high performance requirements attempt to reduce the aerodynamic losses as much as possible in the turbine section. This in turn results in an improvement of the overall thermal efficiency and power output of the engine. As illustrated in FIG. 8, one source of aerodynamic losses is the formation of a variety of vortex flows 2 that may occur as a result of the boundary layer that is formed between a hot working gas flow and an endwall 3 located at the end of an airfoil 4 tending to adhere to the endwall 3, with a resulting lower velocity than the main body of the gas flow. For, example, vortex flows known as horseshoe vortices may form at upstream leading edge locations 5 where the airfoils 4 attach to the endwall 3 and may extend a substantial distance downstream between adjacent airfoils.